verb / noun
sustain
suh-STAYN/səˈsteɪn/
To keep something in effect or continuing.
The gardener waters the young tree regularly to sustain its growth.

Etymology
To “hold up from below” is to support something and keep it from falling. That image extends to keeping an effort going or bearing a hardship, loss, or other burden.
In context
their mother's precious milk must sustain them throughout the winter
More examples
- Small monthly donations sustain the community food pantry.
- The judge sustains the objection and stops the questioning.
- This guitar has enough sustain to let each note linger.
Forms
sustain · sustains · sustained · sustaining
sustenance noun — Food or other support needed for survival.
sustainable adjective — Able to continue with available resources.
Similar words
- maintain
- Emphasizes keeping something at an existing level or condition.
- uphold
- Specifically means confirming a ruling or supporting its validity.
- prolong
- Emphasizes making something last longer than it otherwise would.